Flagyl ER (Metronidazole)

This medicine is called Flagyl (metronidazole). It belongs to a group of medicines known as antibiotics/antiprotozoals. In Australia, it is prescribed by a clinician to treat certain bacterial and protozoal infections.

What Is Metronidazole?

It can be used to:

• treat serious infections caused by susceptible anaerobic bacteria (for example, intra-abdominal infections, skin and skin structure infections, gynaecological infections, bacteraemia/septicaemia, central nervous system infections, lower respiratory tract infections, and endocarditis);
• treat trichomoniasis and amoebiasis

Australian clinicians may sometimes prescribe it for other uses as well, depending on local guidelines and individual factors (off-label use).

Pharmacokinetics

After oral use, metronidazole is well absorbed, with peak plasma concentrations reached 1 to 2 hours after taking it. The average elimination half-life in healthy people is about 8 hours. About 20% of the dose is excreted unchanged in the urine. Metronidazole is found in cerebrospinal fluid and other tissues at concentrations similar to those in plasma.

How to Take Metronidazole

Always take this medicine exactly as your doctor has told you. It is important to complete the full course of treatment. How long you need to take it will depend on your condition and the infection being treated.

Check with your doctor or pharmacist if you are not sure.

• Swallow the tablets whole with a drink of water
• Do not crush or chew the tablets
• Take them exactly as prescribed

Typical adult oral regimens based on Australian prescribing information (examples only; your prescriber may individualise dosing):

Paediatric use: safety and effectiveness in children have not been established, except for the treatment of amoebiasis (paediatric dosing is weight-based and should be prescribed by a clinician).

Your doctor will decide how much to take and how often, depending on the type and severity of the infection.

People with Kidney Dialysis

Haemodialysis can remove a substantial amount of metronidazole from the bloodstream. If the dose cannot be timed separately from the dialysis session, your prescriber may consider an extra dose after haemodialysis depending on your clinical situation.

People with Liver Problems

Your doctor may tell you to take a lower dose or take the medicine less often. A dose reduction is recommended in severe hepatic impairment.

If You Take More Metronidazole Than You Should

If you take more than you should, contact your doctor or the nearest hospital emergency department immediately. If possible, take the box, this leaflet, and any tablets left with you so the doctor knows what you have taken.

If You Forget to Take the Dose

If you miss a dose, take it as soon as you remember and then continue as usual. If it is almost time for your next dose, skip the missed dose and continue as usual. Do not take a double dose to make up for a missed dose.

If you have any further questions about using this product, ask your doctor or pharmacist.

Important Safety Information

Do not take Metronidazole Tablets if you are allergic (hypersensitive) to metronidazole or other nitroimidazole derivatives. Signs of an allergic reaction include a rash, trouble swallowing or breathing, and swelling of your lips, face, throat, or tongue.

Alcohol warning: Do not drink alcohol (and avoid products containing propylene glycol) while you are taking metronidazole and for at least 3 days after finishing your course. Drinking alcohol while taking metronidazole may cause unpleasant side effects such as nausea, vomiting, stomach pain, flushing, headache, and cramping.

Pregnancy and Breastfeeding

Tell your doctor before using this medicine if you are pregnant, might become pregnant, or think you may be pregnant.

• Trichomoniasis: metronidazole tablets are contraindicated during the first trimester. If treatment is needed later in pregnancy and other treatment has not worked well enough, the one-day (2 g) regimen should generally be avoided because it results in higher serum levels.
• Other indications: published studies include first-trimester exposure; discuss the risks and benefits with your clinician.
• Breastfeeding: metronidazole passes into breast milk. Because of the potential for tumorigenicity seen in animal studies, a decision should be made whether to stop breastfeeding or stop the medicine. Alternatively, a breastfeeding mother may express and discard milk during treatment and for 24 hours after treatment ends and feed stored human milk or formula.

Ask your doctor or pharmacist for advice before taking any medicine.

Driving and Using Machines

While taking metronidazole, you may feel sleepy, dizzy, or confused, see or hear things that are not there (hallucinations), have fits (convulsions), or have temporary eyesight problems such as blurred or double vision. If this happens, do not drive or use machinery or tools.

Your doctor may want to carry out some tests if you have been taking this medicine for more than 10 days.

Possible Side Effects

Metronidazole is generally well tolerated. Common side effects include nausea, a metallic taste, and stomach upset. Serious nervous system effects, including seizures, encephalopathy, and optic or peripheral neuropathy, have been reported, particularly with prolonged use. Stop taking the medicine and seek medical advice if you develop neurological symptoms such as numbness, tingling, weakness, vision changes, or severe dizziness.

Stop taking metronidazole and see a doctor or go to an Australian hospital straight away if you get swelling of the hands, feet, ankles, face, lips or throat that may cause difficulty swallowing or breathing. You may also notice an itchy, raised rash (hives) or nettle rash (urticaria). This may mean you are having an allergic reaction.

Speak to your doctor straight away if you notice yellowing of the skin or eyes (jaundice), unusual bruising or bleeding, severe tiredness (possible blood effects), or severe stomach pain that may spread through to your back (pancreatitis).

Long-Term Use

Metronidazole has shown tumorigenicity in mice and rats; unnecessary use should be avoided and treatment should be reserved for appropriate indications.

Interactions

Tell your doctor or pharmacist if you are taking, have recently taken, or might take any other medicines. This includes medicines bought without a prescription, including herbal medicines.

• Disulfiram: do not use metronidazole if you have taken disulfiram within the last 2 weeks.
• Alcohol / propylene glycol: avoid during treatment and for at least 3 days after the last dose.
• Warfarin and other coumarin anticoagulants: metronidazole may increase the risk of bleeding; monitoring or dose adjustment may be needed.
• Lithium (may increase lithium toxicity; monitoring may be needed).
• Busulfan (may increase busulfan exposure/toxicity).
• Phenytoin, phenobarbital (may alter metronidazole levels and effects).
• Ciclosporin / tacrolimus (levels may increase; monitoring may be needed).

Storage and Stability: Store below 25°C (77°F) and protect from light.